This invention relates in general to industrial baghouses and more particularly to a method and apparatus for detecting leaks in the individual filter bags of a baghouse.
Continuous emphasis on environmental quality has resulted in increasingly strenuous regulatory controls on industrial emissions. One technique which has proven highly efficient in controlling air pollution has been the separation of undesirable particulate matter from a gas stream by fabric filtration.
Such filtration is carried out in dust collection apparatus which is known in the trade as a baghouse and which operates in essentially the same manner as an ordinary household vacuum cleaner. The baghouse includes a sheet metal housing divided into two chambers, referred to as plenums, by one or more tube sheets. Disposed within openings communicating with the plenums are filters in the form of bags constructed of a suitable fabric. A particle laden gas stream, induced by the action of a fan, flows into one chamber (dirty air plenum) where dust accumulates on the filter bags as the gas passes through the fabric into the other chamber (clean air plenum) and out the exhaust.
Although all baghouses are designed in accordance with the foregoing general principles, there are numerous operational and structural distinctions. For example, one type of baghouse referred to as an inside collection baghouse effects filtration from inside of the filter bags to the outside. In another type of baghouse known as an outside collection baghouse, filtration occurs from outside to inside such that the particulate matter collects on the outside surfaces of the filter bags. The present invention is directed particularly to outside collection baghouses.
The filter bags eventually become worn and develop leaks which hamper their effectiveness in filtering particulate matter from the gas. It is normal practice to regularly replace the entire array of filter bags at scheduled intervals since the majority of the bags reach the end of their useful life at approximately the same time. In addition, there are invariably some bags which become worn prematurely and leak excessively prior to their regularly scheduled replacement. Such defective bags must be quickly located and replaced or repaired in order to maintain the baghouse at peak operating efficiency and in compliance with emissions standards. However, since the baghouse often contains hundreds or even thousands of filter bags, it is extremely difficult to identify the individual bags which are defective.
In the past, it has been the typical practice for maintenance personnel to physically enter the baghouse compartments and visually inspect the filter bags to determine which bags ae defective and then repair or replace them. The time and effort involved in this labor intensive procedure adds significantly to the overall cost of operating the baghouse and to its off-line time, as well as increasing the risk of physical injury to the maintenance crew due to the hostile conditions encountered in the baghouse and the lengthy time periods during which the workers must be physically present therein. Furthermore, visual examination of the filter bags often results in some of the defective bags being overlooked due to human error.
It is thus apparent that there is a need to reduce the time, labor, and safety hazards involved in identifying defective filter bags in an industrial baghouse. The primary goal of the present invention is to meet that need.
More specifically, it is an object of the invention to provide, in an outside collection baghouse, a method and apparatus for quickly and precisely identifying each individual filter bag which leaks to an unacceptable extent.
Another object of the invention is to provide a method and apparatus which takes advantage of the properties of optical glass fibers to monitor the amount of particulate matter contained in a gas stream. The optical glass fibers are able to withstand the high temperatures and other severe conditions that are often encountered within baghouses and in other hostile environments.
Yet another object of the invention is to provide a method and apparatus of the character described which is well adapted for use with a conventional outside collection baghouse without requiring significant modification of the baghouse structure. In this respect, it is important to note that the sensing heads which monitor the bag leakage are conveniently mounted to an existing manifold pipe forming part of the built in cleaning system of the baghouse.
A further object of the invention is to provide a method and apparatus of the character described wherein each individual filter bag can be monitored on a substantially continuous basis to provide a history of the condition of each bag. This faclitates preventive maintenance and decreases the down time of the baghouse, in that bags which are likely to fail can be identified and replaced or repaired prior to actual failure and during regularly scheduled maintenance operations.
An additional object of the invention is to provide an apparatus of the character described which is simple and economical to construct and install.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.